This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-153791, filed on May 28, 2002, the entire contents of which are incorporated herein by reference.
The present invention relates to a semiconductor testing apparatus for conducting a probing test on a semiconductor device or a substrate.
To effectively test a plurality of circuits formed on a semiconductor wafer, a probing card has 600 to 800 probing pins. Some of the probing cards manufactured presently have more than 1000 probing pins, adjacent ones of which have a spacing of 40 micrometers or less therebetween.
Since an electronic product, such as a cellular phone or a vehicle-mounted element, is used within a relatively wide temperature range, a circuit employed in such an electronic product is also tested over a wide range of temperatures. In a probing test, it is necessary to bring the probing pins into contact with the circuits substantially uniformly independently of a testing temperature.
Generally, in the step of manufacturing a semiconductor device, a probing test is conducted to test the conduction of a wafer. In the probing test, a plurality of probing pins are brought into contact with a plurality of corresponding pads formed on the wafer at a predetermined pressure. The various characteristics of the semiconductor device are measured in accordance with a probing test program.
The probing pins each elongate at a high test temperature and are shortened at a low test temperature. Accordingly, a pressure of contact between the pad and the probing pin varies, thus making the probing test unstable conventionally. The following will describe a conventional testing method by which an influence of a temperature variation in length of the probing pins is reduced.
FIG. 1 is a flowchart of a conventional probing test. FIG. 2 shows a conventional semiconductor testing apparatus 100. The semiconductor testing apparatus 100 includes a chuck 90 on which a wafer W is placed, a probing card 91 having probing pins 92, and a heater 93 for heating the wafer W.
When the probing test starts, the semiconductor testing apparatus 100 holds the chuck 90 at a predetermined testing temperature after heating with the heater 93 in step S91. In step S92, the semiconductor testing apparatus 100 moves the chuck 90 to a position which is separate downward from the probing card 91 by a predetermined spacing, for example, 500 micrometer. The chuck 90 radiates heat to pre-heat the probing pins 92. The pre-heating time ranges from a few minutes to several tens of minutes corresponding to the size of the probing card 91.
In step S93, the semiconductor testing apparatus 100 monitors the tip of the probing pin 92 and the upper surface of the wafer W using a camera (not shown) to simultaneously calculate the height of the chuck 90 when the tip of the probing pin 92 is brought into contact with the upper face of the wafer W.
In step S94, the semiconductor testing apparatus 100 moves the chuck 90 to the height thus calculated and brings the tip of the probing pin 92 into contact with the wafer W and then conducts a conduction test.
It is to be noted that since in the conventional semiconductor testing apparatus 100, the probing pin 92 is pre-heated indirectly in the position which is separate from the chuck 90, its temperature is saturated before the probing pin 92 reaches the testing temperature. The temperature of the probing pin 92, therefore, is lower than the testing temperature, or the temperature of the wafer W.
FIG. 3 is a graph for showing the relationship between the pre-heating time and the height of the tip of the probing pin 92. The height of the tip of the probing pin 92 was measured along the z-axis of FIG. 2 in a condition where the probing card 91 is fixed. As the pre-heating time is prolonged, the probing pin 92 is elongated by heating, resulting in a decrease in the height of the tip thereof. At a time T11, the probing pin 92 has temperature saturation and so stops elongating, thus causing the height of the tip also to stop decreasing. From the time T11 on, the tip is kept at a substantially constant height. A fluctuation xcex94H in the height of the tip owing to pre-heating is about a few tens of micrometers.
During the conduction test, the probing pin 92 is in contact with the wafer W, so that the probing pin 92 is heated by the wafer W to the testing temperature. Therefore, the probing pin 92 elongates further, thus decreasing the height of the tip thereof. Accordingly, a pressure of contact between the probing pin 92 and the wafer W varies greatly during the conduction test (step S95).
In the case of cooling the wafer W down to the testing temperature in order to conduct a probing test, on the other hand, a cooling circuit is used instead of the heater 93. In this case, the probing pin 92 is pre-cooled above the chuck 90 and so shrinks, thus increasing the height of the tip thereof. Furthermore, indirect pre-cooling causes the temperature of the probing pin 92 to become higher than that of the wafer W.
FIG. 4 is an illustration for showing a pin trace formed by contact between the probing pin 92 and the wafer W.
At the middle row in FIG. 4 is shown a pin trace formed in the test at the normal temperature. In this case, the pin trace stayed substantially in a constant position at a time immediately after contact of the probing pin 92 with the wafer W, at a time ten minutes after contact, and at a time of contact in the next position. This is because the temperatures of the probing pin 92 and the wafer W do not vary even when they come in contact with each other.
At the upper row in FIG. 4, on the other hand, is shown a pin trace in the test at a high temperature. In this case, although immediately after contact, the pin trace has a shift in position corresponding to the elongation of the tip of the probing pin 92 owing to pre-heating, the pin trace geometry stays the same as that at the normal temperature. However, as the probing pin 92 is heated by contact with the wafer W to the testing temperature, the probing pin 92 elongates, so that the pin trace expands and becomes large.
At the lower row in FIG. 4 is shown a pin trace formed in the test at a low temperature. In this case, although immediately after contact, the pin trace has a shift in position corresponding to the shortening of the tip of the probing pin 92 owing to pre-cooling, the pin trace geometry stays the same as that at the normal temperature. However, as the probing pin 92 is cooled by contact with the wafer W down to the testing temperature, the probing pin 92 shortens, so that the pin trace is shortened and small.
In the conventional semiconductor testing apparatus 100, therefore, the pressure of contact between the probing pin 92 and the wafer W is unstable, thus likely to give rise to poor contact.
In a conduction test, the probing pin 92 is brought into contact with an electrode (pad) formed on the wafer W. If slippage (scrubbing quantity) of the probing pin 92 is large, the pin trace goes out of the relatively small electrode into a bonding region, thus deteriorating the strength thereof.
Japanese Laid-open Patent Publication No. Hei 5-152389 discloses a probing card and a test bench which have a heating body (or cooling body) buried therein. The heating body (or cooling body) causes the probing card (probing pin) and the test bench to have the same temperature. Accordingly, a fluctuation of a probing pin temperature owing to contact between the probing pin and the wafer is suppressed to suppress the elongation of the probing pin. It is necessary, however, to provide the heating body (or cooling body) for each probing card, so that costs are increased for testing and the manufacture of the semiconductor testing apparatus. Furthermore, the heating body in the probing card is electrified, so that test results may be affected by noise.
It is an object of the present invention to provide a semiconductor testing apparatus which can conduct a test stably on a semiconductor device. It is another object of the present invention to provide a semiconductor testing apparatus which can bring a probing pin into contact with a semiconductor device at a stable pressure.
To achieve the above object, the present invention provides an apparatus for testing a test piece. The apparatus includes a test bench for supporting the test piece while maintaining the test piece at a predetermined testing temperature, and probing pins which are brought into contact with the test piece. A heat transfer block is brought into contact with the probing pins to adjust a temperature of the probing pins to the testing temperature.
A further perspective of the present invention is a method for testing a semiconductor wafer by contacting a plurality of probing pins to the semiconductor wafer. The method includes maintaining the wafer at a predetermined testing temperature, maintaining a heat transfer block at the testing temperature, contacting the tips of the plurality of probing pins to the heat transfer block until a temperature of the plurality of probing pins reaches the testing temperature, and contacting the plurality of probing pins to the wafer.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.